Enhanced photocatalytic and antibacterial activity of ZnO with rice field crab chitosan and plectranthus amboinicus extract

Abstract

Recently, there has been considerable interest in the development of hybrid nanomaterials for health and photocatalytic applications. This study describes the ecofriendly strategy for synthesis of zinc oxide (ZnO) nanoparticles immobilized chitosan (CS) obtained by deacetylation of rice field crab Paratelphusa hydrodromous shells in presence of Plectranthus amboinicus leaf extract (PLE). The resulting CS-ZnO-PLE hybrid nanocomposites were characterized by FT-IR, XRD, UV–Vis-DRS, HR-SEM, TEM, TGA and BET analysis. The HR-SEM study reveals that the CS-ZnO shows hexagonal structure after intercalation of PLE, their structure changed to hierarchical flower-like structure. Presence of reactive functional groups in the chitosan and phytochemicals such as thymol, carvacrol, p-cymene, β-caryophyllene, α-pinene, β-pinene, 1,8-cineole etc in the leaf extract plays a major role in the stabilization of the CS-ZnO-PLE hybrid nanocomposite. Spectroscopic findings reveal that photon energy from sunlight induces an electron that can be transferred from photoexcited chitosan to the conduction band of ZnO NP, which induces the production of reactive oxygen species (ROS) such as H2O2, ●OH and ●O2− are responsible for effective antibacterial and photocatalytic activities. The CS-ZnO-PLE hybrid nanocomposite shows enhanced photocatalytic degradation on methylene blue (∼98.97%) and drimarene red (∼87.43%) than CS-ZnO 67.53% and 30.46% respectively in the duration of 1 h exposure. The antibacterial activity was investigated in terms of inhibition zones using S.aureus and E.Coli bacterial strains and their inhibition zones were found to be 21 and 20 nm. These results provide valuable information for development of alternative chitosan material from rice field crab shells for high efficient photocatalytic and antibacterial activity with metal oxides.